1. Field of the Invention
The present specification relates to a method and an apparatus for measuring a position, more particularly, to a method and an apparatus for measuring a position by cooperation.
2. Related Art
The localization has been largely researched in order to provide the location based service (LBS) of a mobile station as recently the smart phones get spread widely. Also, for performing the Beam Forming by making use of Directional antenna, the base station is able to increase the network capacity through the space diversity and interference management by regulating the direction and the power with the reference of the position of the mobile station, in case that the base station acknowledges the location of the mobile station.
However, the biggest problem in the present localization of the mobile station is that the power consumption of the mobile station is large. In order to perform the localization to the accuracy required by the mobile station and the network, it is necessary to utilize GPS, but GPS consumes large power. As an example, in case a mobile station performs the GPS localization continuously over 3 hours, the power of a mobile station is exhausted.
Accordingly, a method of localization which is not using GPS but effective in power has been largely researched. The following four methods are the examples.
1. A Method for Measuring the Position Using Physical Tools
This is a method, when a mobile station uses a cellular network or a wireless LAN, the mobile station receives a cellular signal or a wireless LAN signal form a base station or an AP of the wireless LAN and then roughly detects the position of the mobile station using intensity of the signal.
For this method, it is more effective in the aspect of power consumption than the localization utilizing GPS, but the error range is very large as much as 100 to 3000 m. Accordingly, a method such as an advanced forward link trilateration (AFLT) is suggested to decrease the error range of the method described above, the AFLT is a method for measuring location using the triangulation method by receiving signal from at least three base stations which are near to a mobile station or an AP of the wireless LAN. However, the AFLT also has a drawback in that the error range is still large as much as 50 to 200 m since the cellular signal or the wireless LAN signal are both multiple path signals.
2. A Method for Measuring the Position Using Indirect Tools
This is a method for measuring the position of a mobile station indirectly by utilizing several sensors built-in the mobile station. The sensors for measuring the position are such as an accelerometer, a digital compass, an angle meter, and so on. However, this method has drawbacks in those an additional sensor is required by the station and the accuracy of measuring the position is not so good.
3. A Method for Measuring the Position by Optimizing GPS/WiFi/Cell ID
This is a method which can use different localization methods according to the location of a mobile station. For example, if a mobile station is outdoors where is good to receive the GPS signals, it is effective to utilize the GPS.
However, if a mobile station is indoors, it is unable to measure the accurate position by using GPS. Rather, in this case, it results in additional power consumption to receive the GPS signal. In addition, if situation is not good to receive the GPS signal (if the accuracy is not good), the power consumption may be decreased by increasing the period to measure GPS. Accordingly, it is the optimal way of selecting a method of the position measurement (by using GPS or WiFi or cell ID) which is fit to the conditions of the mobile terminal according to its circumstances.
4. A Method for Measuring the Position Utilizing Sociality
This is a method in which localization indoors is possible by utilizing human mobility, when a person meets another person, by exchanging information stored in each mobile station, which is traced up to now. However, since the method utilizing the sociality presupposes several limited conditions and several assumptions, still further research is necessary in application of the localization technology in real surroundings.